1. Field of Invention:
This invention relates to stabilization of an organic substrate against light and, more particularly, it is concerned with stabilization of organic compounds, in particular organic dyes, against light.
2. Discussion of the State of the Art:
In general, it is well known that organic substrates such as organic dyes tend to undergo color deterioration or discoloration. In the field of inks, fiber-dyeing or color photography, numerous investigations have been conducted to prevent such color deterioration or discoloration of organic dyes by light, or to improve their light fastness. The present invention can be used to a great advantage for improving the light fastness of the above-described organic substrates.
The term "organic substrate material" or "organic substrate" as they are used in this specification include not only materials which appear to be colored or colorless to the human eye under sunlight, but also include materials having an absorption maximum in the visible region such as optically brightening agents, and materials having an absorption maximum in the infrared region. In the present invention, organic substrates include organic compounds having an absorption maximum in the range of from about 300 nm in ultraviolet region to about 800 nm in infrared region.
The present invention is particularly directed to improving the light fastness of organic substrate materials occurring in photographic materials, e.g., color films, prints, etc., in colored polymers useful as agricultural vinyl cover sheets, umbrellas, tents, etc.; of fluorescent whitening agents; and dyed textiles, etc.
The term "dye" or "dyestuff" as used in this specification includes organic materials appearing colored to the human eye under sunlight.
The term "light" as used herein means electromagnetic radiation of wavelength less than about 800 nm, and includes ultraviolet rays of less than about 400 nm, visible light waves of about 400 nm to about 700 nm, and infrared rays of about 700 nm to about 800 nm.
Organic substrates such as dyes or dyestuffs tend to suffer color deterioration or discoloration when exposed to light, and there have been many reported methods for reducing the color failure or discoloration, or methods for improving the light fastness of the substrates. For example, U.S. Pat. No. 3,432,300 describes that light fastness of such organic compounds as indophenol, indoaniline, azo and azomethine dyes against visible and ultraviolet light can be improved by mixing them with a phenol type compound having a fused hetero ring system.
In the field of silver halide photographic light-sensitive materials, azomethine dyes or indoaniline dyes are generally formed through the reaction between an oxidation product of an aromatic primary amine developing agent and a color former or color coupler as described in G. E. K. Mees and T. H. James; The Theory of the Photographic Process (published by Macmillan Co. in 1967), chap. 17. Many methods have been known for improving the stability of the images made by these dyes, or color images, against light. For example, quinone derivatives have been used as described in U.S. Pat. Nos. 2,360,290, 2,418,613, 2,675,314, 2,701,197, 2,704,713, 2,728,659, 2,732,300, 2,735,765, 2,710,801, 2,816,028, British Pat. No. 1,363,921, etc., gallic acid derivatives described in U.S. Pat. Nos. 3,457,079, 3,069,262, Japanese Patent Publication No. 13,496/68, etc., p-alkoxyphenols described in U.S. Pat. Nos. 2,735,765 and 3,698,909, and chroman or coumaran derivatives described in U.S. Pat. Nos. 3,432,300, 3,573,050, 3,574,627, 3,764,337, 3,574,626, 3,698,909, 4,015,990, etc. However, these compounds are not satisfactory, though they show the effect of preventing color failure or discoloration of color images to some extent.
Also, British Pat. No. 1,451,000 describes the method for improving stability of organic substrates against light by using azomethine quenching compounds having an absorption maximum in a more bathochromic region than that of the base compounds. However, this method is disadvantageous because the azomethine quenching compounds themselves are strongly colored and they exert detrimental influences on the hue of the base material.
In addition, the use of metal complexes for preventing photo deterioration of polymers is described in J. Polym. Sci., Polym. Chem. Ed., 12, 993 (1974) by J. P. Guillory and R. S. Becker, and in J. Polym. Sci., Polym. Let. Ed., 13, 71 (1975) by R. P. R. Ranameera and G. Scoot. Further, methods of stabilizing dyes with metal complexes are described in Japanese Patent Application (OPI) No. 87,649/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) and Research Disclosure 15162 (1976). However, these complexes do not have a large effect and, in addition, they are not sufficiently soluble in organic solvents such that they can be dissolved in a high enough amount to obtain the fullest color deterioration prevention. Further, these complexes are themselves strongly colored, they adversely affect the hue and purity and organic substrates, in particular dyes, when added in a large amounts.